Mullein

Copperbox revision 566.

Some more work on the Haskore interface, where I've tried to work from the Music type rather than the Performance type.

But... I'm not sure this is a valid direction. Haskore doesn't carry around information that is very useful for notation output. For instance, there is no representation of chords within Haskore's data structures - chord's are notes joined with the parallel combinator. I've tried to reconstruct chords by searching for notes with the same onset and duration, but the code to do this is very convoluted.